Coronal Prominence Cavity

Coronal Prominence Cavity

  Prominences are regions of cool, condensed plasma supported by twisted magnetic field lines that globally wrap around an axial magnetic field, called a  magnetic flux rope. Most of the flux rope volume is filled with depleted coronal plasma and forms a transitory cavity – a dark elliptical or semi-circular region that appears empty from our viewpoint. White-light coronagraph observations suggest that cavity density is approximately half the density of the surrounding streamers. However, the plasma properties within the cavities are not uniform, they exhibit temperature substructures that have been observed in multiple wavelengths.

Tuned to observe emission in the extreme ultraviolet (EUV or XUV), NASA’s Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO) provides high-definition imagery of the Sun in seven wavelength passbands. Each of the wavelengths highlight a specific aspect of the solar surface and atmosphere, for example; the dark elliptical structure of the coronal cavity, and outer bright streamers are most visible in AIA 211 Å (Fe XIV), and AIA 193 Å (Fe XII, XXIV) channels, as shown below:

The AIA 171 Å (Fe IX) channel also shows the fine structure of loops, plus the central prominence:

In the 304 Å (He II) channel only the chromospheric features are visible:

More information:

Thermal Properties of a Coronal Cavity (PDF)

SDO/AIA Detection of Solar Prominence Formation Within a Coronal Cavity 

Modeling Coronal Cavities

Image Credit: NASA/SDO/LMSAL